1. Field of the invention
The present invention relates to an optical connector for optical fiber cables.
2. Description of the Prior Art
One of known optical connectors for optical fiber cables has construction as shown in FIG. 1. This optical connector is arranged to insert ferrules 1 and 2, in which optical fibers 10 of optical fiber cables are located and held along the center lines of the ferrules 1 and 2, into a sleeve 3 from both ends of the sleeve 3 so that the ends of the ferrules 1 and 2 contact each other and to thereby connect the ends of the optical fibers.
For the above-mentioned optical connector, it is indispensable to arrange that both optical fibers are accurately aligned with each other, i.e., they come accurately into a straightline. For this purpose, it is essential to arrange that the outer surfaces of the ferrules 1 and 2 are accurately cylindrical and the optical fibers are located accurately on the center lines of the ferrules 1 and 2, the inner surface of the sleeve 3 is also accurately cylindrical and, when the ferrules 1 and 2 are inserted to the sleeve 3, the inner surface of the sleeve 3 contacts the outer surfaces of the ferrules 1 and 2 perfectly closely so that there occurs as far as possible no clearance between said inner surface and said outer surfaces. As a result, the above-mentioned optical connector has such disadvantage that the air in the sleeve 3 does not go out easily when inserting the ferrules 1 and 2 from both ends of the sleeve 3 and, consequently, the ferrules cannot be inserted smoothly.
As a method for eliminating the above-mentioned disadvantage, a small hole 4 may be provided to the sleeve 3 as shown by broken lines in FIG. 1 so that the air goes out through said small hole 4. Even when this method is adopted, it is still not easy to insert the ferrules to the sleeve because of friction between the inner surface of the sleeve and outer surfaces of the ferrules. Moreover, when the sleeve is to be made of synthetic resin, it is difficult to form a sleeve having such small hole.